1. Field of the Invention
The invention relates to the field of metallurgy, especially of wire drawing, and is directed to a method and device for forming and/or coating rod-shaped metal material with lubricants of solid to pasty consistency.
2. Description of the Related Art
In the forming of metal material by means of drawing, solid, semisolid and liquid lubricants are used to produce a lubricant coat on the material to be formed.
In a known process and apparatus for applying solid or semisolid lubricants for cold forming of metal materials, the material to be formed is introduced into a closed chamber containing a lubricant that has been liquefied under the influence of pressure and/or temperature (DD 147 209). The disadvantage of this method and this apparatus consists in that the utilized lubricant has a low viscosity in its liquefied state. This limits the range of possible variations with respect to coating thickness, and a metal material which is coated in this manner can pass through only one or only a few forming steps in view of the meager coating thicknesses (dividing layers) that can be achieved between the two friction partners represented by the forming die and the material to be formed. Moreover, problems arise with respect to the sealing of the inlet nozzle, also as a result of the low viscosity of the lubricant.
Further, methods and apparatus are known in which wire drawing is effected hydrostatically. In one of these devices, the wire passes through a pressure chamber containing a liquid lubricant before entering the drawing stone or drawing die. The lubricant pressure is generated via a pump. For sealing, another drawing die is used as a sealing nozzle at the entrance side of the pressure chamber (J. Schiermeyer, Dissertation TU Clausthal 1979; U.S. Pat. No. 3,413,832). Hydrodynamic lubrication conditions are to be produced in, the main drawing die by this construction of the device.
In the prior art, the sealing of the pressure chamber by means of the sealing nozzle causes problems, since additional lubrication must be carried out in order to realize small forming changes with this sealing nozzle. Another disadvantage consists in that a wire which is already lubricated must be fed to the device. Another disadvantage consists in that the material formed by this device can generally not be used for additional subsequent forming steps without receiving a new coating of lubricant.